All publications herein are incorporated by reference to the same extent as if each individual publication or patent application was specifically and individually indicated to be incorporated by reference. The following description includes information that may be useful in understanding the present invention. It is not an admission that any of the information provided herein is prior art or relevant to the presently claimed invention, or that any publication specifically or implicitly referenced is prior art.
Significant narrowing of epicardial coronary arteries due to atherosclerotic disease or acute embolic obstruction can impede blood flow and oxygen to the myocardium resulting in acute myocardial infarction (AMI). Reperfusion therapy is the standard of care for restoring blood flow to the ischemic myocardial tissue. However, reperfusion therapies are also associated with post-infarct complications that are often associated with fatal heart failure. Most heart failures have an origin in ischemic heart disease and fatalities from it are largely related to Sudden Cardiac Death (SCD). In majority of cases, SCD is triggered by the onset of cardiac arrhythmias, an abnormally rapid heart rate originating in the ventricle and/or atria. If undetected and untreated, this can degenerate into asystole leading to hemodynamic impairment causing death.
Although there are diagnostic and therapeutic strategies for managing and treating ischemic heart disease, these strategies have limited value for distinguishing individual patients at risk for arrhythmias and SCD. The symptoms of ventricular arrhythmias (VA) are palpitations, chest pain, presyncope and syncope. In post-myocardial infarction patients or patients with VA symptoms, a 12-lead ECG, Holter monitoring and loop recorders are used to detect cardiac arrhythmias. However, there are no diagnostic strategies for predicting SCD before the onset of symptoms accompanying cardiac arrhythmias.
The spectrum of therapies also has limited benefits. Antiarrhythmic drugs are frequently prescribed to suppress potential cardiac arrhythmia triggers, but most patients experience serious side effects and more than 40% of patients experience sustained VA recurrence within two years of starting the therapy. Moreover, a majority of anti-arrhythmia medications have pro-arrhythmic potential in patients with structural heart disease, thus, the current ACC (American College of Cardiology) guidelines recommend that antiarrhythmic drugs other than β-blockers should not be used to treat VA unless the patient is protected by an implantable cardioverter-defibrillator (ICD). Cardioversion by shock therapy can be achieved by external electrical defibrillation or internally via an ICD that continuously monitors for and detects episodes of VA. However, ICD therapy is a non-curative approach for patients with VA. It is associated with significantly decreased quality of life associated with VA symptoms and distress of anticipating ICD activation. Radiofrequency ablation offers a potential curative therapy, however the major challenge is the identification of the location of the VA substrate.
Reperfusion hemorrhage is a common consequence of re-establishing epicardial blood flow into severely ischemic myocardium. To date, the long-term effects of hemorrhagic infarcts on electrical conduction in the heart have not been studied. The inventor demonstrates that reperfusion and non-reperfusion hemorrhage leads to deposition of iron particulates within chronic infarcts and examines their role in mediating cardiac arrhythmias (abnormal and rapid beating of heart originating in the ventricle).